1. Field of the Invention
The present invention relates to a backlight device and a method of fabricating the same, and more particularly, to a direct-type backlight device and a method of fabricating the same for a liquid crystal display.
2. Discussion of the Related Art
In general, cathode ray tubes (CRTs) are commonly employed as display devices for televisions, ATM machines, and information terminals. However, CRTs fail to meet the current trend of miniature light weight electronic products due to their size and weight. Thus, efforts have been made to study and develop various types of display devices as substitutions for CRTs, such as liquid crystal display (LCD) devices, plasma display panels (PDPs), electro-luminescence display (ELD) devices, and vacuum fluorescent displays (VFDs). For example, LCD devices have been actively developed as flat display panels in laptop computers, desktop computers, and large-sized information displays because of their high quality image, light weight, small thickness, compact size, and low power consumption. Most LCD devices are passive devices in which images are displayed by controlling an amount of light input from an outside light source. Thus, a separate light source (backlight device) is generally employed for irradiating a LCD.
There are two types of backlight device, an edge light-type and a direct-type, based upon arrangement of the cylindrical fluorescent lamp within the device. An edge light-type backlight device has a lamp unit installed at a side portion of a light guiding plate for guiding light. Further, the lamp unit includes a lamp for emitting light, a lamp holder inserted at both ends of the lamp for protecting the lamp, and a lamp reflective plate for enclosing an outer circumference of the lamp, such that the reflective plate reflects the light generated from the lamp toward the light guiding plate. Alternatively, lamp units can be installed at opposing side portions of the light guiding plate to form a dual edge light-type backlight device, such that if one lamp unit fails to turn ON, the luminance of the screen is lowered, but an image can still be displayed as a whole on a LCD panel. Moreover, the edge light-type backlight devices are commonly employed in small-sized LCD devices of laptop computer and desktop computers because they produce uniform light having high endurance.
A direct-type backlight device has a plurality of lamps arranged in series to directly irradiate an entire surface of a LCD panel. The direct-type backlight devices are mainly used in large-sized LCD devices (20 inches or more), and have higher efficiency of light usage and longer operational lifetime than the edge light-type backlight devices. However, LCD devices employing the direct-type backlight device are more susceptible to a failed lamp, such that if one lamp unit fails, the portion where the lamp is not turned ON becomes remarkably dark and a portion of an image may be lost on a LCD panel. Accordingly, the lamps of the direct-type backlight devices are frequently replaced.
FIG. 1 is a perspective view of an edge light-type backlight device according to the related art, and FIG. 2 is a perspective view of a connector connected with a fluorescent lamp of an edge light-type backlight device according to the related art. In FIG. 1, an edge light-type backlight device of a LCD includes a plurality of fluorescent lamps 1, an outer case 3 for fixedly supporting the fluorescent lamps 1, and a light scattering system 5a, 5b, and 5c arranged between the fluorescent lamps 1 and the LCD panel (not shown). The light scattering system 5a, 5b, and 5c prevents the shape of the fluorescent lamps 1 from appearing on a display surface of the LCD panel, and uniformly distribute light generated from the fluorescent lamps 1. The light scattering system 5a, 5b, and 5c includes a plurality of diffusion sheets and diffusion plates. Further, a reflective plate 7 is formed on an inner bottom surface of the outer case 3 to reflect the light generated from the fluorescent lamps 1 toward the display surface of the LCD panel, thereby maximizing the luminance of the LCD panel.
In FIG. 2, a fluorescent lamp 1 is a cold cathode fluorescent lamp having internal electrodes 2 and 2a at the ends thereof, such that the fluorescent lamp 1 emits light when a power is applied to the electrodes 2 and 2a. In FIG. 1, the ends of the fluorescent lamp 1 are inserted in openings formed at opposing faces of the outer case 3. Power incoming lines 9 and 9a are connected to the ends of the fluorescent lamp 1 and to a connector 11 for transferring a lamp driving power to the fluorescent lamp 1 from a driving circuit (not shown).
However, in the aforementioned backlight device, a connector is necessary for every fluorescent lamp, such that the interconnection of the plurality of fluorescent lamps becomes complicated. Also, to decrease the thickness of the backlight device, a further step of bending the power incoming lines is needed when the power incoming lines are connected to the connector, thereby increasing production time and production cost. Furthermore, an opening of the outer case has to be made to hold the fluorescent lamp and to expose the electrodes of the fluorescent lamp, thereby making maintenance and repair of the fluorescent lamp difficult. Moreover, the outer case confines an effective luminous area generated from light emitted from the fluorescent lamp, such that the effective luminous area is narrow and the luminance at an adjacent portion to ends of the fluorescent lamp becomes unstable.